In their maximal generality, simplification operations in HOL Light (as invoked
by SIMP_TAC) are controlled by a `simpset'. Given a list of theorems thl
and a simpset ss, the call AUGMENT_SIMPSET thl ss augments the state of the
simpset, adding the theorems as new rewrite rules and also making any
provers in the simpset process the new context appropriately.